Cell Structure 2

Endosymbiotic theory

Endosymbiotic theory

Theory that mitochondria and chloroplasts are evolutionary remnants of bacteria that became symbiotic with early single-celled eukaryotes.

Mitochondria

Organelles that generate nearly all of the ATP for eukaryotic cells through the Kreb's cycle and electron transport chain of cellular respiration.

Chloroplasts

Conducts photosynthesis in plant cells. Two outer membranes, and a third membrane system (thylakoids). The convoluted membrane forms flattened and stacked sacs.

Peroxisomes

Organelles that contain enzymes (oxidases) that strip hydrogens from various compounds and transfer them to O2, producing H2O2. Bounded by single membrane. Missing from humans and primates.

Cytoskeleton

A network of fibers that give the cell structural rigidity and allow for various types of cellular movement.

Microtubules

Straight, hollow rods of repeating tubulin molecules that make up the centrioles of centrosomes and act as rails for organelles. Nine triplets arranged in a ring. Also the base of flagella and cilia of eukaryotic cells

Intermediate filaments

Composed of diverse keratin proteins, these filaments provide the basic framework for the entire cytoskeleton and fix organelle positions.

Microfilaments

Composed of two long chains of actin monomers, these filaments resist tensional stress on cell shape and support cells specialized for membrane transport. Muscle contraction (strands of myosin ‘walk’ along acting filaments shortening muscle cell). Actin-myosin complexes also responsible for pinching in animal cells

Cilia and flagella

Structures responsible for the locomotion of eukaryotic cells, with cilia working like oars and flagella exhibiting an undulating motion. Inside structure is a “9+2” arrangement of microtubules, with each doublet connected to dynein sidearms

Plasmodesmata

gated plant cell wall channels that allow the trafficking of molecules between cells and play important roles during plant development and in the orchestration of cellular and systemic signaling responses during interactions of plants with the biotic and abiotic environment.

Basal body

A structure structurally identical to a centriole that anchors cilia and flagella to the cell.

Extracellular matrix (ECM)

A structure found in animal cells that is involved in support, adhesion, movement, and regulation of cellular and gene function. Contains collagen and proteoglycan complexes.

Gap junction

clusters of intercellular channels that allow direct diffusion of ions and small molecules between adjacent cells

Desmosomes

anchors of intermediate filaments that fasten cells tightly together

Tight junctions

sealants that prevent leakage of fluid from top of cell layer to bottom